Methods of fabricating multi-region u-shaped composite structures

ABSTRACT

Methods of fabricating a multi-region U-shaped composite structure, the methods comprising the steps of laying up a first composite material on a first tool piece to form a first sidewall, laying up the second composite material on a second tool piece tool to form a second sidewall, re-orienting the first tool piece and the second tool piece to a consolidation orientation, laying up the third composite material to form a nose wall, and overlapping at least a portion of the third composite material with at least a portion of the first composite material and at least a portion of the second composite material.

BACKGROUND

Composite U-shaped structures with high depth-to-opening aspect ratiospreclude several layup options such as laser projection due to limitedfabrication accessibility. Bridging in nose areas is also common due tothe long fiber draw distances during debulking and due to the practiceof clamping sidewalls of the structures. Furthermore, such compositeU-shaped structures employ homogenous architecture, which necessitatescompromises in the nose areas or the sidewalls.

SUMMARY

Embodiments of the present invention solve the above-mentioned problemsand other problems and provide a distinct advance in the art offabricating composite U-shaped composite structures. More particularly,embodiments of the invention provide methods of fabricating multi-regionU-shaped composite structures that afford improved accessibility duringsidewall layup and permit more complex structure architecture.

An embodiment of the invention is a method of fabricating a multi-regionU-shaped composite structure via a female two-piece tool. First, a firstsurface film (lightning protection, wear protection, or the like) isdeposited on a first layup surface of a first tool piece and a secondlayup surface of a second tool piece with the first tool piece and thesecond tool piece being separated and in a sidewall layup orientation. Asecond surface film is then deposited on the first surface film. Asidewall base carbon fiber layer is then laid up on the second surfacefilm on the first tool piece and the second tool piece.

First and second composite materials are then laid up in layers on thesidewall base carbon fiber layers to form a first sidewall and a secondsidewall. The first composite material and second composite material arelaid up so that each layer exposes a portion of the layer below it toform a tapered end. The composite material layup may be performed viaautomated fiber placement, hand layup assisted with laser projection,ply template hand layup, or any other suitable automated or assistedlayup. The composite material layup may incorporate prepreg material ordry fiber in preparation for resin infusion. An ultrasonic knife may beused to reduce AFP tolerance stack-up and effect between 25% to 50%scarf joint size reduction.

The first tool piece and second tool piece are then reoriented from thesidewall layup orientation to a consolidation orientation (i.e., aU-shape orientation). The first tool piece and second tool piece arethen attached to each other. The first layup surface and the secondlayup surface form a single essentially seamless surface with a spacebetween the first sidewall and the second sidewall. Importantly, anaspect ratio of the depth of the first sidewall and/or second sidewallto the width of the space therebetween may be approximately or at least1, 1.5, 2, or higher, such that it would be difficult to create thefirst sidewall and second sidewall via the above techniques without thetool pieces first being separated.

A third surface film is then deposited on the nose portion of the secondlayup surface. A fourth surface film is then deposited on the thirdsurface film. A base fiberglass fabric layer is then laid up on thefourth surface film.

A nose filler is then laid in the middle of the nose layup region of thesecond layup surface. The nose filler may be a radius filler adhesivewith or without fibers or similar malleable material or component. Anose base carbon fiber layer is then laid up over the nose filler andthe base fiberglass fabric layer.

A third composite material is then laid up in layers on the nose basecarbon fiber layer to form the nose wall. The third composite materialis laid up so that each layer overlaps an exposed layer of the firstcomposite material and second composite material, thereby forming slipplanes (and hence scarf joints) between the nose wall and the firstsidewall and between the nose wall and the second sidewall. Thecomposite material layup forming the nose wall may be performed by hand,ply by ply, or by a suitable technique. The composite material layup mayincorporate dry fiber or prepreg material. The third composite materialmay be woven preform or woven plies for improved impact resistance.

Sidewall cap carbon fiber layers are then laid up over the firstcomposite material and second composite material. A nose wall cap carbonfiber layer is then laid up over the third composite material. Sidewallcap fiberglass fabric layers are then laid up over the sidewall capcarbon fiber layers. A nose wall cap fiberglass fabric layer is thenlaid up over the nose wall cap carbon fiber layer.

The nose wall and/or first and second sidewalls are then debulked, whichmay be performed via a debulking tool. The debulking tool mayincorporate a vacuum system, which may be integrated into the two-piecetool.

The first sidewall, second sidewall, and nose wall may then be co-cured.To that end, the first composite material, second composite material,and third composite material may be co-cure compatible.

The first tool piece and second tool piece are then separated from eachother. The multi-region U-shaped structure is then removed from one ofthe tool pieces. It may also be possible to remove the multi-regionU-shaped structure without separating the tool pieces.

Another embodiment is a method of fabricating a multi-region U-shapedcomposite structure via a female three-piece tool. First, a firstsurface film (lightning protection, wear protection, or the like) isdeposited on a first layup surface of a first tool piece and a secondlayup surface of a second tool piece with the first tool piece and thesecond tool piece separated and in a sidewall layup orientation. Asecond surface film is then deposited on the first surface film. Asidewall base carbon fiber layer is then laid up on the second surfacefilm.

A first composite material and second composite material is then laid upin layers on the sidewall base carbon fiber layers to form a firstsidewall and a second sidewall. The first composite material and secondcomposite material may be laid up so that each layer exposes a portionof the layer below it to form a tapered end. The composite materiallayup may be performed via automated fiber placement, laser projection,ply template layup, or any other suitable automated or assisted layup.The composite material layup may incorporate resin infusion or prepregmaterial. An ultrasonic knife may be used to reduce AFP tolerancestack-up and effect between 25% to 50% scarf joint size reduction.

A third surface film is then deposited on a third layup surface of athird tool piece, a first auxiliary layup surface of a first auxiliarycomponent attached to the third tool piece, and a second auxiliary layupsurface of a second auxiliary component attached to the third tool pieceopposite the first auxiliary component. A fourth surface film is thendeposited on the third surface film.

A base fiberglass fabric layer is then laid up on the fourth surfacefilm. A nose filler is then laid up in the middle of the third layupsurface. The nose filler may be a radius filler adhesive with or withoutfibers or similar malleable material or component. A nose base carbonfiber layer is then laid up over the nose filler and the base fiberglassfabric layer.

A third composite material is then laid up in layers on the nose basecarbon fiber layer to form a nose wall. The composite material layupforming the nose wall may be performed by hand ply by ply, preformed ina separate offline process, or by any other suitable technique. Thethird composite material may be woven preform or woven plies forimproved impact resistance. The composite material layup may incorporateresin infusion or prepreg material.

The first tool piece and second tool piece are then reoriented from thesidewall layup orientation to a consolidation orientation. The firstauxiliary component and second auxiliary component are also removed fromthe third tool piece. The first tool piece and second tool piece arethen attached to the third tool piece. The first layup surface, thesecond layup surface, and the third layup surface should form a singleessentially seamless surface.

Layers of the third composite material should overlap the layers of thefirst composite material and the second composite material therebyforming slip planes (and hence scarf joints) between the nose wall andthe first sidewall and between the nose wall and the second sidewall.Importantly, an aspect ratio of the depth of the first sidewall and/orsecond sidewall to the width of the space therebetween may beapproximately or at least 1, 1.5, 2, or higher, such that it would bedifficult to create the first sidewall and second sidewall via the abovetechniques without the first and second tool pieces first beingseparated.

Sidewall cap carbon fiber layers are then laid up over the firstcomposite material and second composite material of the first sidewalland second sidewall. A nose wall cap carbon fiber layer is then laid upover the third composite material of the nose wall. Sidewall capfiberglass fabric layers are then laid up over the sidewall cap carbonfiber layers. A nose wall cap fiberglass fabric layer is then laid upover the nose wall cap carbon fiber layer.

The nose wall is then debulked, which may be performed via a debulkingtool. The debulking tool may incorporate a vacuum system, which may beintegrated into the three-piece tool.

The first sidewall, second sidewall, and nose wall may then be co-cured.To that end, the first composite material, second composite material,and third composite material may be co-cure compatible.

The first tool piece, second tool piece, and third tool piece are thenseparated from each other. The multi-region U-shaped structure is thenremoved from the third tool piece. It may also be possible to remove themulti-region U-shaped structure without separating the tool pieces.

The above methods are described in terms of outer mold line (OML) layuputilizing female tooling. Structural plies can also be laid up via innermold line (IML) layup mandrel utilizing male tooling and the plies canbe transferred from the layup mandrel to the female, cure tool. Otherfeatures such as the nose filler and lightning strike material (e.g.,Expanded Copper Foil (ECF) material) may subsequently be applied in acure tool.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

Other aspects and advantages of the present invention will be apparentfrom the following detailed description of the embodiments and theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a perspective view of a two-piece tool assembled in accordancewith an embodiment of the invention;

FIG. 2 is an elevation view of the two-piece tool of FIG. 1 in apre-assembled stage;

FIG. 3 is an elevation view of the two-piece tool of FIG. 1 in anassembled stage;

FIG. 4 is a close-up elevation view of the two-piece tool of FIG. 1;

FIG. 5 is a flow diagram depicting certain steps of a method offabricating a multi-region U-shaped composite structure via thetwo-piece tool of FIG. 1;

FIG. 6 is a perspective view of a three-piece tool assembled inaccordance with another embodiment of the invention;

FIG. 7a is an elevation view of a first piece of the three-piece tool ofFIG. 6 in a pre-assembled stage;

FIG. 7b is an elevation view of a second piece of the three-piece toolof FIG. 6 in a pre-assembled stage;

FIG. 7c is an elevation view of a third piece of the three-piece tool ofFIG. 6 in a pre-assembled stage;

FIG. 8 is an elevation view of the three-piece tool of FIG. 6 in anassembled stage;

FIG. 9 is a close-up elevation view of the three-piece tool of FIG. 6;

FIG. 10 is a flow diagram depicting certain steps of a method offabricating a multi-region U-shaped composite structure via thethree-piece tool of FIG. 6;

FIG. 11 is a close-up elevation view of the three-piece tool of FIG. 6utilized in accordance with another embodiment of the invention; and

FIG. 12 is a flow diagram depicting certain steps of a method offabricating a multi-region U-shaped composite structure via thethree-piece tool as depicted in FIG.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

Embodiments of the present invention are directed to methods offabricating multi-region U-shaped composite structures via two-piece andthree-piece tools. The multi-region U-shaped composite structures may beleading edges, trailing edges, rotor blades, horizontal stabilizers,vertical stabilizers, nacelle inlets, and other aircraft components.

Turning to FIGS. 1-3, a two-piece tool 10 for use in one embodiment isillustrated. The two-piece tool 10 broadly comprises a first tool piece12 and a second tool piece 14.

The first tool piece 12 may include a support structure 16 and a firstlayup surface 18. The first tool piece 12 may be configured to be movedfrom a sidewall layup orientation to a consolidation orientation. Thefirst tool piece 12 may also be configured to be connected to the secondtool piece 14 in the consolidation orientation.

The support structure 16 may include forklift tine geometry, hoist ringgeometry, or other features for moving and handling the first tool piece12. The support structure 16 may include ribs, frame plates, and othercomponents for providing rigidity. The support structure 16 may alsoinclude connection geometry 22 such as bolt holes, interlocking tabs,clamps, or the like for connecting the first tool piece 12 to the secondtool piece 14. The connection geometry 22 may include a sealing area forforming a vacuum-tight connection between the first tool piece 12 andsecond tool piece 14 for bagging, consolidation, and curing.

The first layup surface 18 may be a gradually-sloped smooth surface forlaying up materials to form a first sidewall 102. The first layupsurface 18 may include a plurality of concave or convex curves. Thefirst layup surface 18 may also curve in multiple dimensions to form acomplex shape. The first layup surface 18 may have a depth (inconsolidation orientation) smaller or larger than a depth of the secondlayup surface.

The second tool piece 14 may include a support structure 24 and a secondlayup surface 26. The second tool piece 14 may be configured to be movedfrom a sidewall layup orientation to a consolidation orientation. Thesecond tool piece 14 may also be configured to be connected to the firsttool piece 12 in the consolidation orientation.

The support structure 24 may include forklift tine geometry 28, hoistring geometry, or other features for moving and handling the second toolpiece 14. The support structure 24 may include ribs, frame plates, andother components for providing rigidity. The support structure 24 mayalso include connection geometry 30 such as bolt holes, interlockingtabs, clamps, or the like for connecting the second tool piece 14 to thefirst tool piece 12. The connection geometry 30 may include a sealingarea for forming a vacuum-tight connection between the first tool piece12 and second tool piece 14 for bagging, consolidation, and curing.

The second layup surface 26 may be a gradually-sloped smooth surface forlaying up materials to form a second sidewall 104 and a nose wall 106.The second layup surface 26 may include a plurality of concave or convexcurves. The second layup surface 26 may also curve in multipledimensions to form a complex shape. The second layup surface 26 may havea depth (in consolidation orientation) smaller or larger than a depth ofthe first layup surface. The second layup surface 26 may specificallyinclude a nose layup region 32 for laying up materials to form the nosewall 106. The nose layup region 32 may have increased curvature (smallerradii) compared to other portions of the second layup surface 26 andcompared to the first layup surface 18. The nose layup region 32 mayalso curve in multiple dimensions to form a complex shape. In oneembodiment, the nose layup region 32 forms an edge (seen as a point inelevation view). The second layup surface 26 may terminate in the noselayup region such that the second layup surface 26 and the first layupsurface 18 form a continuous curve when the first tool piece 12 and thesecond tool piece 14 are positioned adjacent each other and connected.

Turning to FIG. 5, and with reference to FIGS. 1-4, a method offabricating a multi-region U-shaped composite structure 100 via atwo-piece tool will now be described in detail. The method will bedescribed with reference to two-piece tool 10, but other two-piece toolsmay be used.

First, a first surface film 108 (including embedded lightning protectionsuch as expanded copper foil (ECF), wear protection, or the like) may bedeposited on the first layup surface 18 and the second layup surface 26with the first tool piece 12 and the second tool piece 14 separated andin a sidewall layup orientation, as shown in block 200. The firstsurface film 108 may be SM905, SM905ECF, or similar material. A secondsurface film 110 (additional lightning protection, wear protection, oran adhesive) may then be deposited on the first surface film 108, asshown in block 202. The second surface film 110 may be SM905, SM905ECF,or similar material. A sidewall base carbon fiber layer 112 (e.g.,carbon PW) may then be laid up on the second surface film 110, with someof the second surface film 110 being exposed, as shown in block 204.

First composite material 114 and second composite material 116 may thenbe laid up in layers on the sidewall base carbon fiber layer 112 to formthe first sidewall 102 and the second sidewall 104, as shown in block206. The first composite material 114 and second composite material 116may be laid up so that some of the sidewall base carbon fiber layer 112is exposed. The first composite material 114 and second compositematerial 116 may also be laid up so that each layer exposes a portion ofthe layer below it to form a tapered end. The composite material layupmay be performed via automated fiber placement, hand layup assisted withlaser projection, ply template hand layup, or any other suitableautomated or assisted layup. After laying down a ply or multiple plies,trimming the ply or plies with an ultrasonic knife may reduce AFPtolerance stack-up and effect and reduce the size of the scarf joint by25% to 50%.

The first tool piece 12 and second tool piece 14 may then be reorientedfrom the sidewall layup orientation to the consolidation orientation, asshown in block 208. This may require the use of a forklift, liftinghoists, built-in mechanisms, and the like.

The first tool piece 12 and second tool piece 14 may then be attached toeach other via connection geometry 22 of the first tool piece 12 andconnection geometry 30 of the second tool piece 14, as shown in block210. The first layup surface 18 and the second layup surface 26 shouldform a single essentially seamless surface with a space between thefirst sidewall 102 and the second sidewall 104. Importantly, an aspectratio of the depth of the first sidewall 102 and/or second sidewall 104to the width of the space therebetween may be approximately or at least1, 1.5, 2, or higher, such that it would be difficult to create thefirst sidewall 102 and second sidewall 104 because there is limitedspace for the AFP head or for an operator to lay down plies without thetool pieces 12, 14 first being separated.

A third surface film 118 may be deposited on the nose portion of thesecond layup surface 26, as shown in block 212. A fourth surface film120 may then be deposited on the third surface film 118, as shown inblock 214. Portions of the fourth surface film 120 may overlap portionsof the second surface film 110.

A base fiberglass fabric layer 122 may then be laid up on the fourthsurface film 120, as shown in block 216. Portions of the base fiberglassfabric layer 122 may overlap portions of the second surface film 110.

A nose filler 124 may then be laid in the middle of the nose layupregion 32 of the second layup surface 26, as shown in block 218. Thenose filler 124 may be a filler putty or similar malleable material orcomponent.

A nose base carbon fiber layer 126 may then be laid up over the nosefiller 124 and the base fiberglass fabric layer 122, as shown in block220. Portions of the nose base carbon fiber layer 126 may overlapportions of the sidewall base carbon fiber layer 112.

A third composite material 128 may then be laid up in layers on the nosebase carbon fiber layer 126 to form the nose wall 106, as shown in block222. The third composite material 128 may be laid up so that each layeroverlaps an exposed layer of first composite material 114 and secondcomposite material 116 of the first sidewall 102 and second sidewall104, thereby forming slip planes 138A,B between the nose wall 106 andthe first sidewall 102 and between the nose wall 106 and the secondsidewall 104, thus creating two scarf joints. The composite materiallayup forming the nose wall 106 may be performed by hand, ply by ply, orby a suitable technique despite limited access to the space as hinderedby the first tool 12 and second tool 14. The third composite material128 may be woven preform or woven plies, for improved impact resistance.On that point, the third composite material 128 may include thicker oradditional plies compared to the first and second composite materials114, 116. Alternatively, the third composite material 128 may beconstructed or consolidated offline in a separate process and laid up asa single piece.

Sidewall cap carbon fiber layers 130 may then be laid up over the firstcomposite material 114 and second composite material 116 of the firstsidewall 102 and second sidewall 104, as shown in block 224. Portions ofthe sidewall cap carbon fiber layer 130 may overlap portions of thethird composite material 128 of the nose wall 106.

A nose wall cap carbon fiber layer 132 may then be laid up over thethird composite material 128 of the nose wall 106, as shown in block226. Portions of the nose wall cap carbon fiber layer 132 may overlapportions of the sidewall cap carbon fiber layer 130.

Sidewall cap fiberglass fabric layers 134 may then be laid up over thesidewall cap carbon fiber layers 130, as shown in block 228. Portions ofthe sidewall cap fiberglass fabric layers 134 may extend over the thirdcomposite material 128 of the nose wall 106.

A nose wall cap fiberglass fabric layer 136 may then be laid up over thenose wall cap carbon fiber layer 132, as shown in block 230. Portions ofthe nose wall cap fiberglass layer 132 overlap portions of the sidewallcap fiberglass fabric layers 130.

The nose wall 106 and/or first and second sidewalls 102, 104 may then bedebulked, as shown in block 232. This may be performed via a debulkingtool. The debulking tool may incorporate a vacuum system and film orelastomeric material applied to surround the U-shaped structure andcompress the materials. The vacuum system may be integrated into thetwo-piece tool 10.

The first sidewall 102, second sidewall 104, and nose wall 106 may thenbe co-cured, as shown in block 234. To that end, the first compositematerial 114, second composite material 116, and third compositematerial 128 may be co-cure compatible.

The first tool piece 12 and second tool piece 14 may then be separatedfrom each other, as shown in block 236. The multi-region U-shapedstructure 100 may then be removed from the second tool piece 14 (orfirst tool piece 12), as shown in block 238.

The above-described method provides several advantages. For example,layup up composite material on separated tool pieces to form sidewallsimproves access, thereby allowing for the use of layup aids andautomation. Individually fabricating multiple regions also allows forcomplex structure architecture. In particular, nose sections can beformed with high impact resistance materials and techniques, whilesidewalls can be formed with more economical or more suitable sidewallmaterials and techniques, thus reducing overall weight withoutsacrificing functionality.

Furthermore, slip planes between regions improve debulking performance,preventing the composite material from wrinkling or bridging in theradius area. Part removal following co-cure is also easier by separatingtool pieces. The present invention also allows for smaller nose wallradiuses and tighter part tolerances.

Turning to FIGS. 6-9, a three-piece tool 300 for use in anotherembodiment is illustrated. The three-piece tool 300 broadly comprises afirst tool piece 302, a second tool piece 304, a third tool piece 306, afirst auxiliary component 308, and a second auxiliary component 310.

The first tool piece 302 may include a support structure 312 and a firstlayup surface 314. The first tool piece 302 may be configured to bemoved from a sidewall layup orientation to a consolidation orientation.The first tool piece 302 may also be configured to be connected to thethird tool piece 306 in the consolidation orientation.

The support structure 312 may include forklift tine geometry, hoist ringgeometry, or other features for moving and handling the first tool piece302. The support structure 312 may include ribs, frame plates, and othercomponents for providing rigidity. The support structure 312 may alsoinclude connection geometry 318 such as bolt holes, interlocking tabs,clamps, or the like for connecting the first tool piece 302 to the thirdtool piece 306.

The first layup surface 314 may be a gradually-sloped smooth surface forlaying up materials to form a first sidewall 402. The first layupsurface 314 may include a plurality of concave or convex curves. Thefirst layup surface 314 may also curve in multiple dimensions to form acomplex shape. The first layup surface 314 may have a depth (inconsolidation orientation) smaller or larger than a depth of the secondlayup surface.

The second tool piece 304 may include a support structure 320 and asecond layup surface 322. The second tool piece 304 may be configured tobe moved from a sidewall layup orientation to a consolidationorientation. The second tool piece 304 may also be configured to beconnected to the third tool piece 306 in the consolidation orientation.

The support structure 320 may include forklift tine geometry 324, hoistring geometry, or other features for moving and handling the second toolpiece 304. The support structure 320 may include ribs, frame plates, andother components for providing rigidity. The support structure 320 mayalso include connection geometry 326 such as bolt holes, interlockingtabs, clamps, or the like for connecting the second tool piece 304 tothe third tool piece 306.

The second layup surface 322 may be a gradually-sloped smooth surfacefor laying up materials to form a second sidewall 404. The second layupsurface 322 may include a plurality of concave or convex curves. Thesecond layup surface 322 may also curve in multiple dimensions to form acomplex shape. The second layup surface 322 may have a depth (inconsolidation orientation) smaller or larger than a depth of the firstlayup surface.

The third tool piece 306 may include a support structure 328 and a thirdlayup surface 330. The third tool piece 306 may be configured to beconnected to the first tool piece 302 and the second tool piece 304 inthe consolidation orientation.

The support structure 328 may include forklift tine geometry, hoist ringgeometry, or other features for moving and handling the third tool piece306. The support structure 328 may include ribs, frame plates, and othercomponents for providing rigidity. The support structure 328 may alsoinclude connection geometry 334 such as bolt holes, interlocking tabs,clamps, or the like for connecting the third tool piece 306 to the firsttool piece 302 and the second tool piece 304.

The third layup surface 330 may specifically include geometry for layingup materials to form the nose wall 406. The third layup surface 330 mayhave increased curvature (smaller radii) compared to the first layupsurface 314 and the second layup surface 322. The third layup surface330 may also curve in multiple dimensions to form a complex shape. Inone embodiment, the third layup surface 330 forms an edge (seen as apoint in elevation view). The third layup surface 330 may form acontinuous curve with the first layup surface 314 and the second layupsurface 322 when the first tool piece 302 and the second tool piece 304are positioned adjacent and connected to the third tool piece.

The first auxiliary component 308 may include connection geometry 336and a first auxiliary layup surface 338. The connection geometry 336allows the first auxiliary component 308 to be attached to the thirdtool piece 306.

The first auxiliary layup surface 338 may be a gradually-sloped smoothsurface for laying up materials to form a portion of the nose wall 406.The first auxiliary layup surface 338 may include a plurality of concaveor convex curves. The first auxiliary layup surface 338 may also curvein multiple dimensions to form a complex shape.

The second auxiliary component 310 may include connection geometry 340and a second auxiliary layup surface 342. The connection geometry 340allows the second auxiliary component 310 to be attached to the thirdtool piece 306 opposite the first auxiliary component 308.

The second auxiliary layup surface 342 may be a gradually-sloped smoothsurface for laying up materials to form a portion of the nose wall 406.The second auxiliary layup surface 342 may include a plurality ofconcave or convex curves. The second auxiliary layup surface 342 mayalso curve in multiple dimensions to form a complex shape.

Turning to FIG. 10, and with reference to FIGS. 6-9, a method offabricating a multi-region U-shaped composite structure 400 via athree-piece tool will now be described in detail. The method will bedescribed with reference to three-piece tool 300, but other three-piecetools may be used.

First, a first surface film 408 (lightning protection, wear protection,or the like) may be deposited on the first layup surface 314 and thesecond layup surface 322 with the first tool piece 302 and the secondtool piece 304 separated and in a sidewall layup orientation, as shownin block 500. A second surface film 410 may then be deposited on thefirst surface film 408, as shown in block 502. A sidewall base carbonfiber layer 412 (e.g., carbon PW) may then be laid up on the secondsurface film 410, with some of the second surface film 410 beingexposed, as shown in block 504.

First composite material 414 and second composite material 416 may thenbe laid up in layers on the sidewall base carbon fiber layer 412 to formthe first sidewall 402 and the second sidewall 404, as shown in block506. The first composite material 414 and second composite material 416may be laid up so that some of the sidewall base carbon fiber layer 412is exposed. The first composite material 414 and second compositematerial 416 may also be laid up so that each layer exposes a portion ofthe layer below it to form a tapered end. The composite material layupmay be performed via automated fiber placement, laser projection, plytemplate layup, or any other suitable automated or assisted layup. Anultrasonic knife may be used to reduce AFP tolerance stack-up and effectbetween 25% to 50% scarf joint size reduction.

With the first auxiliary component 308 and the second auxiliarycomponent 310 attached to the third tool piece 306, a third surface film418 may be deposited on the third layup surface 330, the first auxiliarylayup surface 338, and the second auxiliary layup surface 342, as shownin block 508. A fourth surface film 420 may then be deposited on thethird surface film 418, as shown in block 510. Portions of the fourthsurface film 420 may overlap portions of the second surface film 410.

A base fiberglass fabric layer 422 may then be laid up on the fourthsurface film 420, as shown in block 512. Portions of the base fiberglassfabric layer 422 may overlap portions of the second surface film 410.

A nose filler 424 may then be laid in the middle of the third layupsurface 330, as shown in block 514. The nose filler 424 may be a fillerputty or similar malleable material or component.

A nose base carbon fiber layer 426 may then be laid up over the nosefiller 424 and the base fiberglass fabric layer 422, as shown in block516. Portions of the nose base carbon fiber layer 426 may overlapportions of the sidewall base carbon fiber layer 412.

A third composite material 428 may then be laid up in layers on the nosebase carbon fiber layer 426 to form the nose wall 406, as shown in block518. The third composite material 428 may be laid up so that each layerextends past previously laid layers. The composite material layupforming the nose wall 406 may be performed by hand, ply by ply, or byany other suitable technique. The third composite material 428 may bewoven preform or woven plies for improved impact resistance. On thatpoint, the third composite material 428 may include thicker oradditional plies compared to the first and second composite materials414, 416.

The first tool piece 302 and second tool piece 304 may then bereoriented from the sidewall layup orientation to the consolidationorientation, as shown in block 520. This may require the use of aforklift, lifting hoists, built-in mechanisms, and the like. The firstauxiliary component 308 and the second auxiliary component 310 may alsobe removed from the third tool piece 306, as shown in block 522. Laid upmaterial may be removed from the third tool piece 306 via vacuum orsuction cup overhead mechanical equipment (OHME) before removal of thefirst and second auxiliary components 308, 310.

The first tool piece 302 and second tool piece 304 may then be attachedto the third tool piece 306 via connection geometry 318 of the firsttool piece 302, connection geometry 326 of the second tool piece 304,and connection geometry 334 of the third tool piece 306, as shown inblock 524. The first layup surface 314, the second layup surface 322,and the third layup surface 330 should form a single essentiallyseamless surface. Layers of the third composite material 428 shouldoverlap with the layers of the first composite material 414 and thesecond composite material 416 thereby forming slip planes 438A,B betweenthe nose wall 406 and the first sidewall 402 and between the nose wall406 and the second sidewall 404, thus creating two scarf joints.Importantly, an aspect ratio of the depth of the first sidewall 402and/or second sidewall 404 to the width of the space therebetween may beapproximately or at least 1, 1.5, 2, or higher, such that it would bedifficult to create the first sidewall 402 and second sidewall 404 viathe above techniques without the first and second tool pieces 302, 304first being separated.

Sidewall cap carbon fiber layers 430 may then be laid up over the firstcomposite material 414 and second composite material 416 of the firstsidewall 402 and second sidewall 404, as shown in block 526. Portions ofthe sidewall cap carbon fiber layer 430 may overlap portions of thethird composite material 428 of the nose wall 406.

A nose wall cap carbon fiber layer 432 may then be laid up over thethird composite material 428 of the nose wall 406, as shown in block528. Portions of the nose wall cap carbon fiber layer 432 may overlapportions of the sidewall cap carbon fiber layer 430.

Sidewall cap fiberglass fabric layers 434 may then be laid up over thesidewall cap carbon fiber layers 430, as shown in block 530. Portions ofthe sidewall cap fiberglass fabric layers 434 may extend over the thirdcomposite material 428 of the nose wall 406.

A nose wall cap fiberglass fabric layer 436 may then be laid up over thenose wall cap carbon fiber layer 432, as shown in block 532. Portions ofthe nose wall cap fiberglass layer 436 may overlap portions of thesidewall cap fiberglass fabric layers 434.

The nose wall 406 may then be debulked, as shown in block 534. This maybe performed via a debulking tool. The debulking tool may incorporate avacuum system. The vacuum system may be integrated into the three-piecetool 300.

The first sidewall 402, second sidewall 404, and nose wall 406 may thenbe co-cured, as shown in block 536. To that end, the first compositematerial 414, second composite material 416, and third compositematerial 428 may be co-cure compatible.

The first tool piece 302, second tool piece 304, and third tool piece306 may then be separated from each other, as shown in step 538. Themulti-region U-shaped structure 400 may then be removed from the thirdtool piece 306, as shown in block 540.

The above-described method provides several advantages. For example,layup up composite material on separated tool pieces to form sidewallsimproves access, thereby allowing for the use of layup aids andautomation. Individually fabricating multiple regions also allows forcomplex structure architecture. In particular, nose sections can beformed with high impact resistance materials and techniques, whilesidewalls can be formed with more economical or more suitable sidewallmaterials and techniques, thus reducing overall weight withoutsacrificing functionality.

Furthermore, slip planes between the regions improve debulkingperformance. Part removal following co-cure is also easier by separatingtool pieces. Utilizing a three-piece tool provides more versatility interms of material layup order and slip plane location, direction, andsize. Nose walls and sidewalls can also be fabricated simultaneously,further reducing manufacturing time. The present invention also allowsfor smaller nose wall radiuses and tighter part tolerances.

Turning to FIG. 12, and with reference to FIG. 11, another method offabricating a multi-region U-shaped composite structure 600 via athree-piece tool will now be described in detail. The method will bedescribed with reference to three-piece tool 300, but other three-piecetools may be used.

First, a sidewall base carbon fiber layer 608 may be laid up on thefirst layup surface 314 and the second layup surface 322 with the firsttool piece 302 and the second tool piece 304 separated and in a sidewalllayup orientation, as shown in block 700. This may require the use oframped auxiliary components temporarily attached to the first tool piece302 and second tool piece 304 to support at least a portion of thesidewall base carbon fiber layer 608.

First composite material 610 and second composite material 612 may thenbe laid up in layers on the sidewall base carbon fiber layer 608, asshown in block 702. The first composite material 610 and secondcomposite material 612 may be laid up so that each layer extends pastthe previous layer to form an upwardly tapered end. Again, this mayrequire the use of ramped auxiliary components temporarily attached tothe first tool piece 302 and second tool piece 304. Each ply may be cutafter it is laid up. The composite material layup may be performed viaautomated fiber placement, laser projection, ply template layup, or anyother suitable automated or assisted layup. An ultrasonic knife may beused to reduce AFP tolerance stack-up and effect between 25% to 50%scarf joint size reduction.

Sidewall cap carbon fiber layers 614 may then be laid up over the firstcomposite material 610 and second composite material 612 of the firstsidewall 602 and second sidewall 604, as shown in block 704. Portions ofthe sidewall cap carbon fiber layers 614 may extend past the top layersof the first composite material 610 and second composite material 612.

A nose filler 616 may be laid in the middle of the third layup surface330, as shown in block 706. The nose filler 616 may be a filler putty orsimilar malleable material or component. A nose base carbon fiber layer618 may then be laid up over the nose filler 616, as shown in block 708.

A third composite material 620 may then be laid up in layers on the nosebase carbon fiber layer 618 to form a nose wall 606, as shown in block710. The third composite material 620 may be laid up so that each layerexposes a portion of previously laid layers. The composite materiallayup forming the nose wall 606 may be performed by hand, ply by ply, orby any other suitable technique. The third composite material 620 may bewoven preform or woven plies for improved impact resistance.

A nose wall cap carbon fiber layer 622 may then be laid up over thethird composite material 620 of the nose wall 606, as shown in block712. The nose wall cap carbon fiber layer 622 may expose portions of thetop layer of the third composite material 620.

The ramped auxiliary components may then be removed from the first toolpiece 302 and second tool piece 304 if used during some of the abovelayup steps, as shown in block 714. The first tool piece 302 and secondtool piece 304 may then be reoriented from the sidewall layuporientation to the consolidation orientation, as shown in block 716.This may require the use of a forklift, lifting hoists, built-inmechanisms, and the like.

The first tool piece 302 and second tool piece 304 may then be attachedto the third tool piece 306, as shown in block 718. The first layupsurface 314, the second layup surface 322, and the third layup surface330 should form a single essentially seamless surface. Layers of thefirst composite material 610 and second composite material 612 shouldoverlap with the layers of the third composite material 620 therebyforming slip planes 624A,B between the nose wall 606 and the firstsidewall 602 and between the nose wall 606 and the second sidewall 604,thus creating two scarf joints. Importantly, an aspect ratio of thedepth of the first sidewall 602 and/or second sidewall 604 to the widthof the space therebetween may be approximately or at least 1, 1.5, 2, orhigher, such that it would be difficult to create the first sidewall 602and second sidewall 604 via the above techniques without the first andsecond tool pieces 302, 304 first being separated.

The nose wall 606 may then be debulked, as shown in block 720. This maybe performed via a debulking tool. The debulking tool may incorporate avacuum system. The vacuum system may be integrated into the three-piecetool 300.

The first sidewall 602, second sidewall 604, and nose wall 606 may thenbe co-cured, as shown in block 722. To that end, the first compositematerial 610, second composite material 612, and third compositematerial 620 may be co-cure compatible.

The first tool piece 302, second tool piece 304, and third tool piece306 may then be separated from each other, as shown in step 724. Themulti-region U-shaped structure 600 may then be removed from the thirdtool piece 306, as shown in block 726.

The above method illustrates that slip planes between a nose wall andcorresponding sidewalls can taper toward the nose wall or away from thenose wall as desired. The slip planes could also taper in the samedirection. Other characteristics such as slip plane angle and position(i.e., spacing from an apex of the nose) can also be effected asdesired.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:

1. A method of fabricating a multi-region U-shaped composite structure,the method comprising the steps of: laying up a first composite materialon a first tool piece of a multi-piece tool to form a first sidewall;laying up a second composite material on a second tool piece of themulti-piece tool to form a second sidewall; re-orienting the first toolpiece and the second tool piece to a consolidation orientation;positioning the first tool piece and the second tool piece to form aspace between the first sidewall and the second sidewall; laying up athird composite material on the first tool piece and the second toolpiece in the space to form a nose wall; and overlapping at least aportion of the first composite material and at least a portion of thesecond composite material with at least a portion of the third compositematerial.
 2. The method of claim 1, wherein the first tool piece and thesecond tool piece are positioned adjacent to one another during the stepof positioning the first tool piece and the second tool piece to form aspace between the first sidewall and the second sidewall.
 3. The methodof claim 1, wherein the first tool piece and the second tool piece arepositioned on opposite sides of a third tool piece during the step ofpositioning the first tool piece and the second tool piece to form aspace between the first sidewall and the second sidewall, and whereinthe step of laying up a third composite material includes laying up thethird composite material on the third tool piece.
 4. The method of claim1, wherein the step of laying up a third composite material to form thenose wall comprises placing an uncured laminate comprising a pluralityof plies of the third composite material.
 5. The method of claim 1, thelaying up steps including tapering layers of the first compositematerial, the second composite material, and the third compositematerial, the overlapping step including forming slanted slip planesbetween the nose wall and the first sidewall and between the nose walland the second sidewall.
 6. The method of claim 1, the steps of layingup the first composite material and laying up the second compositematerial including at least one of automated fiber placement, hand layupassisted with laser projection, and ply template layup.
 7. The method ofclaim 1, the first sidewall and the second sidewall having a depthgreater than a width of the space.
 8. The method of claim 1, furthercomprising a step of co-curing the first sidewall, the second sidewall,and the nose wall after the overlapping step.
 9. The method of claim 1,the third composite material being different than the first compositematerial and second composite material.
 10. The method of claim 1, thestep of laying up the third composite material being performed ply byply.
 11. The method of claim 1, further comprising a step of separatingthe first tool piece and the second tool piece to remove the compositestructure from the first tool piece and the second tool piece.
 12. Amethod of fabricating a multi-region U-shaped composite structure, themethod comprising the steps of: laying up a first composite material ona first tool piece of a three-piece tool to form a first sidewall;laying up the second composite material on a second tool piece of athree-piece tool to form a second sidewall; laying up a third compositematerial on a third tool piece of the three-piece tool to form a nosewall; re-orienting the first tool piece and the second tool piece to aconsolidation orientation; positioning the third tool piece between thefirst tool piece and the second tool piece to form a space between thefirst sidewall and the second sidewall; positioning the nose wall in thespace formed between the first sidewall and the second sidewall; andoverlapping at least a portion of the third composite material with atleast a portion of the first composite material and at least a portionof the second composite material.
 13. The method of claim 10, the layingup steps including tapering layers of the first composite material, thesecond composite material, and the third composite material, theoverlapping step including forming slanted slip planes between the nosewall and the first sidewall and between the nose wall and the secondsidewall.
 14. The method of claim 10, the steps of laying up the firstcomposite material and laying up the second composite material includingat least one of automated fiber placement, laser projection, and plytemplate layup.
 15. The method of claim 10, the first sidewall and thesecond sidewall having a depth greater than a width of the space. 16.The method of claim 14, further comprising a step of co-curing the firstsidewall, the second sidewall, and the nose wall after the debulkingstep, the first composite material, second composite material, and thirdcomposite material being co-cure compatible.
 17. The method of claim 10,the third composite material being different than the first compositematerial and second composite material.
 18. The method of claim 10, thestep of laying up the third composite material including laying up atleast a portion of the third composite material on first and secondauxiliary pieces removably attached to the third tool piece, the methodfurther comprising a step of removing the auxiliary pieces from thethird tool piece before the positioning step.
 19. The method of claim10, the method further comprising a step of separating the first toolpiece and the second tool piece from the third tool piece to remove thecomposite structure from the first tool piece, second tool piece, andthird tool piece.
 20. A method of fabricating a multi-region U-shapedcomposite structure, the method comprising the steps of: placing a layerof lightning protection on a first tool piece, a second tool piece, anda third tool piece of a three-piece tool; laying up a first compositematerial on the first tool piece via at least one of automated fiberplacement, laser projection, and ply template layup to form a firstsidewall; laying up a second composite material on the second tool piecevia at least one of automated fiber placement, laser projection, and plytemplate layup to form a second sidewall; placing a filler on the thirdtool piece; laying up a third composite material on the third tool pieceand at least a portion of the third composite material on first andsecond auxiliary pieces removably attached to the third tool piece plyby ply to form a nose wall; removing the auxiliary pieces from the thirdtool piece; re-orienting the first tool piece and the second tool pieceto a consolidation orientation; positioning the third tool piece betweenthe first tool piece and the second tool piece so the nose wall is atleast partially positioned in a space between the first sidewall and thesecond sidewall, the first sidewall and the second sidewall having adepth greater than a width of the space; overlapping at least a portionof the third composite material with at least a portion of the firstcomposite material and at least a portion of the second compositematerial to form slanted slip planes between the nose wall and the firstsidewall and between the nose wall and the second sidewall; debulkingthe nose wall; and co-curing the first sidewall, the second sidewall,and the nose wall.